Enclosure Airflow Controller

1. A system, comprising: an enclosure configured to contain a plurality of compute nodes; an airflow controller configured to control a flow of air provided to each of the plurality of compute nodes; wherein the airflow controller is configured to receive unsolicited requests for airflow from each of the compute nodes; wherein the airflow controller is configured to control airflow provided to a given compute node based on the unsolicited airflow requests received from a subset of the compute nodes, including the given node, the subset of the compute nodes being assigned to a same airflow zone by the airflow controller; and a shared communication link coupling the plurality of compute nodes to the airflow controller, wherein the communication link includes a communication link access request signal received by the airflow controller indicating a given compute node has an airflow request, a communication link grant signal asserted by the airflow controller in response to the request signal, and a serial data link configured to propagate the unsolicited airflow requests from the plurality of compute nodes to the airflow controller.

2. The system of claim 1 , wherein the enclosure comprises a plurality of fans configured to provide airflow to the plurality of compute nodes, and the airflow controller is configured to individually control each of the plurality fans based on the unsolicited airflow requests received from the plurality of compute nodes.

3. The system of claim 1 , wherein the compute nodes are configured to detect the enclosure and responsive to the detection provide airflow requests to the airflow controller.

4. The system of claim 1 , wherein the airflow controller is configured to adjust the flow of air provided to each of the plurality of compute nodes at a predetermined interval, the adjustment comprising providing the given compute node with a maximum airflow requested by a compute node from amongst compute nodes forming the subset of the compute nodes including the given node.

5. The system of claim 1 , wherein each of the compute nodes comprises a processor to measure temperature of a component of the compute node, and generate a request for airflow based on the measured temperature.

6. The system of claim 1 , further comprising a plurality of serial data links, each of the plurality of serial data links being assigned to one of the plurality of compute nodes and wherein the communication link access request signal and the communication link grant signal form a pair of signals and wherein the system further comprises a plurality of the pairs, each of the plurality of pairs being assigned to a specific one of the plurality of compute nodes.

7. A method, comprising: receiving unsolicited airflow requests from each of a plurality of compute nodes installed in an enclosure; categorizing each airflow request in accordance with an intra-enclosure airflow zone in which the compute node providing the airflow request is located; controlling a fan in the enclosure to provide an airflow to a given compute node based on all of the airflow requests received during a predetermined time interval from compute nodes located in an airflow zone including the given compute node.

8. The method of claim 7 , further comprising setting an airflow request register to a predetermined minimum non-zero airflow value at the start of an airflow update interval.

9. The method of claim 7 , further comprising determining airflow provided to the given compute node based only on requests for airflow greater than a current airflow value.

10. The method of claim 7 , further comprising determining an airflow to provide based on a maximum airflow request received from compute nodes within an airflow zone within a predetermined interval.

11. The method of claim 7 , further comprising: receiving, by an airflow controller in the enclosure, a request for control of an airflow request communication link from a given one of the plurality of compute nodes; granting, by the airflow controller, control of the communication link to the given compute node; and receiving, by the airflow controller an airflow request from the given compute node.

12. An airflow controller, comprising: a processor; a software system that when executed configures the processor to individually control an airflow provided to each of a plurality of airflow zones within an enclosure comprising the airflow controller; wherein each airflow zone provides airflow to a plurality of compute nodes, and the software system configures the processor to receive unsolicited airflow requests from the plurality of compute nodes; serial airflow request links, each of the serial airflow request links being assigned to one of the plurality of compute nodes, each of the serial airflow request links to propagate unsolicited airflow requests from the plurality compute nodes to the airflow controller; and pairs of grant and request signals, each pair assigned to one of the plurality of compute nodes, wherein the airflow controller selects a single serial airflow request link from the serial airflow request links based on a request for link access to send an airflow requests received from a given compute node.

13. The airflow controller of claim 12 , wherein the software system configures the processor to control a plurality of fans disposed within the enclosure, at least one of the plurality of fans providing airflow to each airflow zone.

14. The airflow controller of claim 12 , wherein the software system configures the processor to select an airflow for a given airflow zone based on a maximum airflow requested by a compute node within the given airflow zone.

15. The airflow controller of claim 12 , further comprising an airflow request register for each airflow zone, wherein the software system configures the processor to periodically set a given airflow request register in accordance with a minimum predetermined fan speed, to determine whether received requests exceed the airflow specified by the current value of the given airflow request register and to overwrite the airflow request register responsive to a determination that a request for airflow exceeds the airflow specified by the current value of the given airflow request register.